Add sample_figures/ngff_images_figure.json

[will-moore]

Add the sample file from gist into this repo...

[will-moore]

cc @jburel Moved the gist demo figure into this repo.
The URL in the File > Open dialog reflects the ome/master branch where the json file will be when this PR is merged.

[jburel]

The link in the README should also be updated so it does not point to the gist under your account

[will-moore]

I didn't update gist links in the README because they are specifically illustrating the gist workflow described there.
If you could create an equivalent gist under ome then I can update to use that?

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[will-moore]

If no objection to the current changes, which can be seen at https://ome.github.io/figure/?file=https://raw.githubusercontent.com/will-moore/figure/refs/heads/figure_json_from_gist/sample_figures/ngff_images_figure.json
then I'd like to get this merged so that I can refer to that sample file in ome master branch from elsewhere.